This circuit is very simple less than 12 component, to build DC to AC converter. The principle of this circuit is generating 50/60Hz frequency by IC CD4047 and the output complement pin 10 and 11 of IC CD4047 to drive MOSFET IRFZ 44 so induction primary transformer is work and get high voltage at out secondary transformer about 220V AC. The output converter wave is still square wave and more close to sine wave with filter C3 220nF.
For more high current output (wattage) use high current battery and the MOSFET must be parallel. For example to get 240W output the battery used is 20A. Or if you use 24V CT transformer you just only use battery 24V/10A. In practice report the commonly is use 9V CT transformer will step up to high voltage output, if using 12V CT transformer were dissatisfied because transformer losses.
